It is known in the art relating to internal combustion engines that the gas charge admitted to the combustion chambers should be compressed to maximum permissible values to obtain fuel efficiency. Varying output engines as used in automobiles achieve variation in power output by regulating the gas charge mass flow. In normal engines, only under full charge mass flow is the charge compressed to maximum permissible values due to the fixed geometric compression ratio, which is designed to accommodate maximum charge mass flow. Yet most driving is done under greatly throttled conditions, resulting in fuel inefficiency under most driving conditions.